A method for directly extracting lithium from lithium-containing brine using an adsorption process.

Abstract

This invention discloses a method for directly extracting lithium from lithium-containing brine using an adsorption process. The pretreated brine is fed into a continuous countercurrent adsorption system containing N-stage continuous overflow adsorption stirred tanks. Lithium is extracted from the lithium-containing brine through N-stage continuous countercurrent adsorption. Then, the washed loaded adsorbent is fed into a continuous countercurrent desorption system containing M-stage continuous overflow desorption stirred tanks. Lithium is desorbed through M-stage continuous countercurrent desorption. The resulting lithium-rich solution is pretreated and then subjected to reverse osmosis, nanofiltration, and further concentration to obtain the final concentrate for preparing the desired lithium product. Compared with traditional lithium extraction processes, this invention has lower equipment requirements and investment costs, higher adsorption and desorption rates, higher adsorbent utilization, and a controllable desorption process, allowing for flexible adaptation to changes in brine lithium concentration and production capacity.

Description

Technical Field

[0001] This invention relates to the field of lithium extraction technology from lithium-containing brine, specifically to a method for directly extracting lithium from lithium-containing brine using an adsorption process. Background Technology

[0002] Lithium is hailed as the "white oil of the future." With the rapid development of the new energy industry and the continuous development and application of high-performance lithium materials, the demand for lithium is increasing daily. The supply of lithium ore resources will become insufficient, while salt lake brines contain abundant lithium resources, accounting for 66% of the world's lithium reserves, and 87% of my country's total lithium reserves. Therefore, the development of lithium resources in salt lake brines is of great significance to the sustainable development of the lithium industry.

[0003] Lithium extraction processes from lithium-containing brines include solvent extraction, precipitation, calcination, membrane separation, and adsorption. Among these, adsorption is currently widely used in the salt lake lithium extraction industry due to its advantages such as high selectivity for lithium, environmental friendliness, and ease of automation.

[0004] The core of the adsorption-based lithium extraction process lies in the adsorbent and the matching adsorption equipment. Regarding adsorbents, currently available materials for this process include organic and inorganic adsorbents, with inorganic adsorbents being more widely used, including aluminum-based, titanium-based, and manganese-based adsorbents. In terms of application methods, adsorbents can be granular or powdered. CN111825152A discloses a powder-based lithium extraction technology where the adsorbent is mixed with brine and then conveyed to a filter press. The press frame has a reciprocating filter cloth, and along the direction of the filter cloth's movement are sequentially arranged a solid-liquid separation zone, a salt washing zone, and a desorption zone. A lithium eluent collection port is located below the desorption zone, ultimately yielding a lithium eluent with a magnesium-to-lithium ratio of less than 1:1. However, this technology suffers from problems such as the fine particle size of the adsorbent powder, difficulty in solid-liquid separation, low adsorbent utilization, and significant leakage during the process. Therefore, most salt lakes currently use granulated adsorbents for lithium extraction. For example, CN110743516A, CN115738892A, and CN115845825A all disclose methods for granulating lithium adsorbents. Furthermore, Salt Lake Industry and Zangge Lithium Industry have used granulated aluminum-based adsorbents for lithium extraction from the Qarhan Salt Lake, Zijin Mining has used granulated titanium-based adsorbents for lithium extraction from the Lagoco Salt Lake, and Tailixin has conducted experimental research on lithium extraction from the Kushui Lake using granulated manganese-based adsorbents. However, the adsorption capacity of adsorbent powder is significantly reduced after granulation. For instance, the working adsorption capacity of manganese-based adsorbent powder can reach 20 mg / g, but after granulation, the saturated adsorption capacity is only 6-8 mg / g. During the column packing operation, due to the influence of fluid linear velocity and adsorption kinetics, the actual working capacity is only 3-5 mg / g. To ensure production capacity, it is necessary to increase the initial investment in equipment and adsorbents.

[0005] Regarding adsorbent-related equipment, current adsorption equipment mainly consists of fixed beds, simulated moving beds, and continuous ion-exchange devices. For example, CN109354043A discloses a method for removing impurities and extracting lithium from ultra-low concentration lithium-containing brine. The adsorption and impurity removal device includes an adsorption tower and a valve array unit, thereby controlling the adsorption, rinsing, and desorption operations of each resin layer. This device generally uses fixed beds or simulated moving beds, but it suffers from problems such as large footprint, complex piping connections, and low adsorbent utilization. CN116377248A discloses a continuous ion-exchange method for reducing the solubility loss of titanium-based adsorbents. This process uses a continuous ion-exchange lithium extraction device, which has advantages such as high automation and high adsorbent utilization compared to fixed beds and simulated moving beds, but requires a large investment. Furthermore, with the aforementioned lithium extraction equipment, due to the fixed defects of the equipment, there is an over-desorption phenomenon of the adsorbent during the desorption process, especially for ion sieve type adsorbents, which may cause accelerated solubility loss of the adsorbent or even scaling and collapse, causing irreversible damage to the adsorbent.

[0006] In summary, current adsorption-based lithium extraction processes suffer from drawbacks such as difficulty in filtering powdered adsorbents and low working adsorption capacity of particulate adsorbents; continuous ion exchange processes are expensive, while fixed-bed and simulated moving-bed processes require large floor space, involve complex equipment connections, and suffer from low adsorbent utilization. There is an urgent need to develop a high-efficiency adsorption-desorption lithium extraction process that is low-investment, simple, and causes minimal damage to the adsorbent, providing technical support for the large-scale application of lithium-containing brine adsorption-based lithium extraction. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention aims to provide a method for directly extracting lithium from lithium-containing brine using an adsorption process.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A method for directly extracting lithium from lithium-containing brine using an adsorption process includes the following steps:

[0010] Step 1: Pre-treat the lithium-containing brine to remove impurities;

[0011] Step 2: The pretreated brine from Step 1 is fed into a continuous countercurrent adsorption system containing N stages of continuous overflow adsorption stirring tanks. Lithium is extracted from the lithium-containing brine through N stages of continuous countercurrent adsorption. The lithium-containing brine is added from the first stage overflow adsorption stirring tank and flows into the next stage overflow adsorption stirring tank. The tail brine flows out from the Nth stage overflow adsorption stirring tank. The unloaded adsorbent is added from the Nth stage overflow adsorption stirring tank and is lifted into the next stage overflow adsorption stirring tank. The loaded lithium adsorbent is discharged from the first stage overflow adsorption stirring tank.

[0012] Step 3: Wash the loaded adsorbent discharged from the first-stage overflow adsorption mixing tank with low-salt water to remove entrained brine;

[0013] Step 4: The washed loaded adsorbent from Step 3 is fed into a continuous countercurrent desorption system containing an M-stage continuous overflow desorption stirring tank. Lithium desorption is achieved through M-stage continuous countercurrent desorption. The loaded adsorbent is added from the M-stage overflow desorption stirring tank and gradually flows to the next stage overflow desorption stirring tank. The empty adsorbent after lithium desorption is discharged from the 1-stage overflow desorption stirring tank. The desorption liquid is added from the 1-stage overflow desorption stirring tank and flows into the next stage overflow desorption stirring tank. The lithium-rich liquid flows out from the M-stage overflow desorption stirring tank.

[0014] Step 5: Return the empty adsorbent discharged from the first-stage overflow desorption mixing tank in Step 4 to Step 2 for recycling;

[0015] Step 6: The lithium-rich solution obtained in Step 4 is first concentrated using reverse osmosis to produce low-salt water and concentrated water. The concentrated water is then treated with nanofiltration to remove calcium and magnesium ions. The nanofiltration permeate is further concentrated using high-pressure reverse osmosis, electrodialysis, solar cell, mechanical steam recompression, or multi-effect evaporation. The final concentrated solution is used to prepare the desired lithium product.

[0016] Further, in step one, the lithium-containing brine includes one or more of the following: salt lake brine, lithium-containing geothermal water, lithium-containing ore leachate, lithium-containing brine generated during oilfield extraction, and lithium-containing leachate generated during lithium battery recycling. The lithium-containing brine is of the chloride type, sodium sulfate subtype, or carbonate type, and the lithium concentration is 50-1000 mg / L. The pretreatment includes one or more of the following: sand filtration, ultrafiltration, microfiltration, flocculation sedimentation, and oxidation, and includes one or more of the following: pH adjustment, sulfate removal, carbonate removal, and heating.

[0017] Further, in step two, the adsorbent is one or a combination of several of the following: molecular sieve-type aluminum-based adsorbent, ion sieve-type manganese-based adsorbent, and ion sieve-type titanium-based adsorbent. The adsorbent is in the form of powder, magnetic powder, or granules obtained by granulation of powder adsorbent. The particle size of the powder or magnetic powder adsorbent is 10μm-1000μm; the particle size of the granular adsorbent is 1000μm-10000μm. The lithium extraction capacity of the adsorbent in the continuous countercurrent adsorption system is adjusted by adding fresh adsorbent purchased externally or produced on-site, or by open-circuit regeneration of adsorbent with degraded performance.

[0018] Furthermore, in step two, the lithium working capacity of the adsorbent is 5-50 mg / g; when the adsorption capacity of the adsorbent decays to 25-50% of the adsorption capacity of the fresh adsorbent, an open circuit and regeneration treatment is performed, and the regeneration treatment is carried out by one or more of the following methods: solid-state sintering, precipitation, and hydrothermal method.

[0019] Further, in step two, N = 2-8. In each overflow adsorption stirring tank, the mass ratio of brine to adsorbent is 2-100:1, and the adsorption temperature is -5-50℃. After the brine and adsorbent are fully contacted by one or more of the following methods: mechanical stirring, aeration stirring, or pump circulation stirring, the adsorbent is separated from the brine by one or more of the following methods: concentration, bag filtration, magnetic separation, and centrifugal filtration. The separated adsorbent is lifted upwards, and the separated brine overflows downwards. The lifting rate of the adsorbent is such that the amount of adsorbent lifted in each overflow adsorption stirring tank within 1 hour is 10-80% of the total mass of the adsorbent in that overflow adsorption stirring tank. The adsorption pH in each overflow adsorption stirring tank is 5-11. Depending on the pH requirements of different adsorbents, the pH of the brine is adjusted before adsorption, or acid or alkali is directly added to each overflow adsorption stirring tank to adjust the pH of the brine.

[0020] Furthermore, in step three, the total dissolved solids (TDS) content in the low-salt water is less than 1000 mg / L, including one or more of reverse osmosis permeate, surface freshwater, or evaporation condensate; the mass of the low-salt water used for washing is 1-10 times the mass of the loaded adsorbent discharged from the first-stage countercurrent adsorption tank.

[0021] Further, in step four, M = 2-8; in each stage of overflow desorption stirring tank, the mass ratio of desorbent to adsorbent is 4-40, the desorption temperature is 5-50℃, and the pH value of the desorbed solution is 2.0-7.0; after the desorbent and adsorbent are fully mixed by one or more of mechanical stirring, aeration stirring, and pump circulation stirring, the adsorbent and desorbent are separated by concentration, filtration, or magnetic separation. The separated adsorbent is lifted upwards, and the separated desorbent overflows downwards; in each stage of overflow desorption stirring tank, the lifting rate of the adsorbent is such that the amount of adsorbent lifted within 1 hour is 50-300% of the total amount of adsorbent in the overflow desorption stirring tank.

[0022] Furthermore, in step four, when the adsorbent is a molecular sieve type adsorbent, a low saline solution is used as the desorption solution.

[0023] When the adsorbent is an ion sieve type adsorbent, an acidic solution is used as the desorption liquid. The acidic solution is prepared by mixing a low-salt water solution, a low-lithium solution, and an acid. The low-lithium solution includes one or more of the following: the washing liquid after desorption of the adsorbent, nanofiltration permeate, electrodialysis desalination water, and high-pressure reverse osmosis permeate. The acid is one or more of the following: hydrochloric acid, sulfuric acid, and nitric acid. The desorption pH in each stage overflow desorption stirring tank is 1.0-5.0.

[0024] The total dissolved solids (TDS) of the low-salinity water is less than 300 mg / L, including one or more of reverse osmosis permeate, surface freshwater, or evaporative condensate.

[0025] Furthermore, in step six, the lithium-rich solution obtained in step four is pretreated before being concentrated using reverse osmosis.

[0026] If the adsorbent is an aluminum-based or titanium-based adsorbent, the pretreatment of the lithium-rich solution includes the removal of suspended solids using an ultrafiltration membrane.

[0027] If the adsorbent is a manganese-based adsorbent, the pretreatment of the lithium-rich solution includes adding alkali to adjust the pH to 7-9 for hydrolysis, followed by aeration oxidation for 2-30 minutes, and then filtration using composite filter media to remove manganese. After manganese removal, the manganese ion concentration in the lithium-rich solution is less than 1 mg / L. Before entering the reverse osmosis concentration stage, the lithium-rich solution after manganese removal is subjected to ultrafiltration membrane to remove suspended solids. The oxidant used for aeration oxidation is one or more of the following: air, a mixture of air and sulfur dioxide, hydrogen peroxide, oxygen, ozone, or chlorine. The composite filter media includes manganese sand and one or more of the following: activated carbon, quartz sand, fiber balls, anthracite, and ceramsite.

[0028] Furthermore, in step six, the low-salt water produced by concentrating the lithium-rich solution using reverse osmosis is returned to step three for washing and / or returned to step four as desorption water;

[0029] The concentrated water produced by reversing osmosis to concentrate lithium-rich solution is then subjected to nanofiltration to remove calcium and magnesium ions, resulting in a lithium ion concentration of 7-10 g / L and a combined calcium and magnesium ion concentration of less than 5 mg / L. The concentrated water obtained by further concentration of nanofiltration permeate has a lithium ion concentration of 25-50 g / L. The nanofiltration concentrate is then dialyzed to further recover lithium. The desalinated water produced by dialysis is returned to the reverse osmosis process, while the concentrated water produced by dialysis is returned to the continuous countercurrent adsorption system in step two.

[0030] The concentrated solution is prepared into lithium products using evaporation crystallization, chemical precipitation, or a combination of ion exchange deep purification, bipolar membrane, and evaporation crystallization processes; the lithium products are crude, chemical-grade, or battery-grade lithium sulfate, lithium chloride, lithium carbonate, lithium phosphate, or lithium hydroxide monohydrate.

[0031] The beneficial effects of this invention are as follows:

[0032] 1) This invention adopts a multi-stage continuous countercurrent adsorption-desorption process, which has lower equipment requirements and lower investment compared with fixed bed, simulated moving bed or continuous ion-exchange adsorption lithium extraction process.

[0033] 2) The present invention has a fast adsorption rate, high adsorbent utilization rate, and controllable desorption process. If it is an ion sieve type adsorbent, the desorption process can achieve continuous acid replenishment and extend the service life of the adsorbent.

[0034] 3) Compared with traditional adsorption lithium extraction processes (fixed bed, simulated moving bed, continuous ion exchange equipment), the adsorbent and brine or desorbent are in instantaneous, multi-dimensional homogeneous contact during adsorption and desorption, resulting in fast adsorption rate and high desorption efficiency. In contrast, in traditional column adsorption and desorption processes, the brine, desorbent and lithium extraction agent are in contact through directional flow of the adsorption column, resulting in lower efficiency. In particular, for ion sieve type adsorbents, there are problems such as low utilization rate of the front-end adsorbent and over-desorption.

[0035] 4) Compared with traditional adsorption lithium extraction processes (fixed bed, simulated moving bed, continuous ion exchange equipment), the continuous countercurrent adsorption-desorption process adopted in this invention can flexibly adapt to changes in brine lithium concentration and production capacity by adjusting brine flow rate, adsorbent concentration in tank and adsorbent lifting speed.

[0036] 5) This invention regenerates the degraded adsorbent, which has the advantages of reusable resources, no need to purchase adsorbent, and low raw material investment costs, which can further increase the economic benefits of enterprises. Attached Figure Description

[0037] Figure 1 This is a general flowchart of the methods in Embodiments 1-4 of the present invention;

[0038] Figure 2 This is a flowchart illustrating the overall countercurrent adsorption process of the methods in Examples 1-4 of the present invention.

[0039] Figure 3 This is a flowchart illustrating the overall countercurrent desorption process of the methods in Embodiments 1-4 of the present invention.

[0040] Figure 4 This is a schematic diagram of the process of lithium-containing brine and adsorbent being lifted during countercurrent adsorption and desorption in the method of Embodiment 1 of the present invention;

[0041] Figure 5 This is a schematic diagram of the process of lithium-containing brine and adsorbent being lifted during countercurrent adsorption and desorption in the method of Embodiment 2 of the present invention;

[0042] Figure 6 This is a schematic diagram of the process of lithium-containing brine and adsorbent being lifted during countercurrent adsorption and desorption in the method of Embodiment 3 of the present invention;

[0043] Figure 7 This is a schematic diagram of the process of lithium-containing brine and adsorbent being lifted during countercurrent adsorption and desorption in the method of Embodiment 4 of the present invention. Detailed Implementation

[0044] The present invention will be further described below with reference to the accompanying drawings. It should be noted that this embodiment is based on the present technical solution and provides detailed implementation methods and specific operation processes, but the protection scope of the present invention is not limited to this embodiment.

[0045] Example 1

[0046] This embodiment provides a method for directly extracting lithium from salt lakes using an adsorption process, such as... Figure 1 As shown, the specific process is as follows:

[0047] (1) Countercurrent adsorption process of manganese-based adsorbent powder

[0048] Manganese-based adsorbent powder (the crystal form of the manganese-based adsorbent is Li) 1.6 Mn 1.6 O4) and pretreated lithium-containing brine (Li 400mg / L, Na 100g / L, K 4.16g / L, Ca 17.7g / L, Mg 1.25g / L, B 0.37g / L, Cl 190g / L, SO4) 2- 0.56 g / L, brine pH 5.8) in a continuous countercurrent adsorption system containing three stages of continuous overflow adsorption stirred tanks. Figure 2 The material comes into contact with the adsorbent. In this embodiment, the pretreatment uses ultrafiltration to remove suspended solids, colloids, macromolecules, and other components and factors that may affect the downstream adsorption from the lithium-containing brine.

[0049] like Figure 2 As shown, brine is added from the first-stage overflow adsorption stirring tank and flows out from the third-stage overflow adsorption stirring tank. Unloaded adsorbent is added from the third-stage overflow adsorption stirring tank and gradually lifted to the next stage overflow adsorption stirring tank. Loaded adsorbent is discharged from the first-stage overflow adsorption stirring tank.

[0050] The separation and flow of brine and adsorbent between the various overflow adsorption mixing tanks are as follows: Figure 4 As shown. The adsorption residence time in each overflow adsorption stirring tank is 20 min, the stirring speed is 100 rpm, the mass ratio of brine to adsorbent is 15:1, and the adsorption temperature is 15℃. During the adsorption process in each overflow adsorption stirring tank, 1% NaOH solution is added to control the adsorption pH value at around 6. During the adsorption process, the adsorbent and brine overflow into the thickener through the overflow port on the overflow adsorption stirring tank. The supernatant in the thickener overflows into the next overflow adsorption stirring tank. 70% (mass percentage) of the adsorbent slurry underflow from the thickener is pumped back into the current overflow adsorption stirring tank, and 30% is pumped into the previous overflow adsorption stirring tank. After the adsorption in the third-stage overflow adsorption stirring tank, the lithium concentration in the tail brine was 16 mg / L. After the adsorption in the second-stage overflow adsorption stirring tank, the lithium concentration in the brine after adsorption was 148 mg / L. After the adsorption in the first-stage overflow adsorption stirring tank, the lithium concentration in the brine after adsorption was measured to be 343 mg / L. The calculated adsorption capacity of the manganese-based adsorbent powder was 19.2 mg / g, and the lithium adsorption rate was 96%.

[0051] (2) Countercurrent desorption process of manganese-based adsorbent powder

[0052] The countercurrent desorption process of the supported adsorbent is as follows Figure 3 As shown, similar to the adsorption process, the desorption process is completed by an overflow desorption stirred tank and a thickener. The loaded adsorbent, washed with low-salt water, is fed into a continuous countercurrent desorption system containing three stages of overflow desorption stirred tanks. The pH of the first and second stages of overflow desorption stirred tanks is controlled at 1.2 by adding 1 mol / L hydrochloric acid, and the pH of the third stage overflow desorption stirred tank is controlled at approximately 3-4 by adding 1 mol / L hydrochloric acid.

[0053] The initial acid concentration of the desorption solution is 0.1 mol / L. It flows into the first-stage overflow desorption stirring tank and then into the next-stage overflow desorption stirring tank. The lithium-rich solution flows out from the third-stage overflow desorption stirring tank. The loaded adsorbent is added from the third-stage overflow desorption stirring tank and then gradually lifted into the next-stage overflow desorption stirring tank. The unloaded adsorbent is discharged from the first-stage overflow desorption stirring tank, realizing three-stage continuous countercurrent lithium extraction and desorption.

[0054] After desorption in each stage of the overflow desorption mixing tank, the adsorbent and desorbate overflow through the overflow port into the thickener. The supernatant desorbate in the thickener overflows into the next stage of the overflow desorption mixing tank. 80% (mass percentage) of the adsorbent slurry from the underflow of the thickener is pumped to the previous stage of the overflow desorption mixing tank, and 20% is returned to the current stage's overflow desorption mixing tank. The desorption time in each stage of the overflow desorption mixing tank is 20 minutes, the stirring speed is 100 rpm, the mass ratio of desorbate to adsorbent is 8:1, and the desorption temperature is 25℃. During the desorption process in each stage of the overflow desorption mixing tank, the pH value is controlled at around 1.5 by adding 1 mol / L HCl solution.

[0055] After desorption in the third-stage overflow desorption stirred tank, the lithium concentration of the outflowing lithium-rich liquid was 1.91 g / L. After desorption in the second-stage overflow desorption stirred tank, the lithium concentration of the outflowing desorbed liquid was 1.63 g / L. After desorption in the first-stage overflow desorption stirred tank, the lithium concentration of the outflowing desorbed liquid was 526 mg / L. The calculated desorption capacity of the manganese-based adsorbent powder was 19.1 mg / g, and the lithium desorption rate was 99%.

[0056] (3) Lithium-rich liquid purification and concentration process and lithium carbonate preparation process

[0057] The obtained lithium-rich solution (Li 1.91 g / L, Na 202 mg / L, K 56 mg / L, Ca 108 mg / L, Mg 15.3 mg / L, Mn 53 mg / L) was first adjusted to pH 9 by adding alkali, and then aerated for 2 minutes. After aeration, it was filtered using a composite filter media (comprising manganese sand and activated carbon). The manganese ion concentration in the lithium-rich solution after manganese removal was less than 1 mg / L. Before entering the reverse osmosis concentration stage, the lithium-rich solution after manganese removal was further purified by ultrafiltration to remove suspended solids. After reverse osmosis concentration and then nanofiltration to remove calcium and magnesium, the lithium ion concentration was 7.5 g / L, sodium ion concentration was 0.79 g / L, potassium ion concentration was 0.22 g / L, and the combined calcium and magnesium ion concentration was 3.2 mg / L. The nanofiltration permeate was further concentrated to a lithium concentration of 50 g / L using MVR (solar cell or mechanical vapor recompression technology). Then, the purified solution was obtained by deep removal of calcium, magnesium and boron using resin (calcium and magnesium ion concentrations totaled 2 mg / L, boron concentration 1 mg / L). The purified solution was then subjected to lithium precipitation at 85°C using a 28% sodium carbonate solution to obtain lithium carbonate product. The lithium concentration in the lithium precipitation mother liquor was measured to be 1.25 g / L.

[0058] (4) Regeneration of manganese-based adsorbent powder attenuation

[0059] After a long cycle of multiple cycles, when the adsorption capacity of the manganese-based adsorbent powder drops to 10 mg / g, the adsorbent is regenerated. The process involves mixing the degraded manganese-based adsorbent powder with lithium carbonate, resulting in a lithium-manganese molar ratio of 1:1 in the mixed sample. The uniformly mixed sample is then calcined in a muffle furnace at approximately 500°C for 6 hours. After calcination, a lithium manganese oxide precursor is obtained, which is then activated to obtain the manganese-based adsorbent powder.

[0060] Example 2

[0061] This embodiment provides a method for directly extracting lithium from salt lakes using an adsorption process, such as... Figure 1 As shown, the specific process is as follows:

[0062] (1) Countercurrent adsorption process of titanium-based adsorbent particles

[0063] Titanium-based adsorbent particles (particle size 1000μm-5000μm, dry basis bulk density 0.4g / cm³) were used. 3 The titanium-based adsorbent (Li₂TiO₃ crystal form) and the pretreated lithium-containing brine (Li₂ 30 mg / L, Na 15.3 g / L, K 2.23 g / L, Ca 23 mg / L, Mg 0.76 g / L, B 0.71 g / L, Cl) were used. - 11.59 g / L, SO4 2-19.14 g / L, carbonate 3 g / L, brine pH 9.1) were fed into a multi-stage countercurrent adsorption system containing eight continuous overflow adsorption stirred tanks. Figure 2 In this embodiment, the pretreatment adopts a sand filtration process, the purpose of which is to remove suspended solids, colloids, macromolecules and other components and influencing factors that may affect the downstream adsorption in the lithium-containing brine.

[0064] Brine is added from the first-stage overflow adsorption stirring tank, flowing sequentially to the next stage and exiting from the eighth-stage overflow adsorption stirring tank. Unloaded adsorbent is added from the eighth-stage overflow adsorption stirring tank, flowing sequentially to the previous stage. Loaded adsorbent is discharged from the first-stage overflow adsorption stirring tank. The adsorption time in each stage of the overflow adsorption stirring tank is 30 minutes, the stirring speed is 200 rpm, the brine to adsorbent mass ratio is 10:1, and the adsorption temperature is 10℃.

[0065] like Figure 5 As shown, after the adsorption in each overflow adsorption mixing tank is completed, the brine overflows through the overflow port of the overflow adsorption mixing tank to the next overflow adsorption mixing tank. A filter screen is used at the overflow port to prevent the adsorbent from overflowing with the brine. The adsorbent is drawn from the bottom of the overflow adsorption mixing tank to the next overflow adsorption mixing tank through an air lifter. By controlling the flow rate of the air lifter, it is ensured that 40% of the adsorbent by mass in a single overflow adsorption mixing tank is lifted to the next overflow adsorption mixing tank within 30 minutes.

[0066] After the adsorption in the eighth-stage overflow adsorption stirred tank, the lithium concentration in the tail brine was 5.8 mg / L. After the adsorption in the seventh-stage overflow adsorption stirred tank, the lithium concentration in the brine after adsorption was 37.8 mg / L. After the adsorption in the sixth-stage overflow adsorption stirred tank, the lithium concentration in the brine after adsorption was 63 mg / L. After the adsorption in the fifth-stage overflow adsorption stirred tank, the lithium concentration in the brine after adsorption was 95 mg / L. After the adsorption in the fourth-stage overflow adsorption stirred tank, the lithium concentration in the brine after adsorption was 120 mg / L. After the adsorption in the third-stage overflow adsorption stirred tank, the lithium concentration in the brine after adsorption was 148 mg / L. After the adsorption in the second-stage overflow adsorption stirred tank, the lithium concentration in the brine after adsorption was 177 mg / L. After the adsorption in the first-stage overflow adsorption stirred tank, the lithium concentration in the brine after adsorption was 211 mg / L. The calculated adsorption capacity of the titanium-based adsorbent particles was 5.61 mg / g, and the lithium adsorption rate was 97.5%.

[0067] (2) Countercurrent desorption process of titanium-based adsorbent particles

[0068] The countercurrent desorption process of the supported adsorbent is as follows Figure 3As shown, similar to the adsorption process, the desorption process is completed by an overflow desorption stirred tank and an air lift. The loaded adsorbent is washed with low-salt water and then fed into a continuous countercurrent desorption system containing three stages of overflow desorption stirred tanks. In the first and second stages of overflow desorption stirred tanks, the pH is controlled at 1.5 by adding 1 mol / L hydrochloric acid, while in the third stage, the pH is controlled at approximately 3-4 by adding 1 mol / L hydrochloric acid.

[0069] The initial acid concentration of the desorption solution is 0.1 mol / L. It flows into the first-stage overflow desorption stirred tank and sequentially into the next-stage overflow desorption stirred tank, exiting from the third-stage overflow desorption stirred tank. The loaded adsorbent is added from the third-stage overflow desorption stirred tank and progressively lifted to the next-stage overflow desorption stirred tank. Unloaded adsorbent is discharged from the first-stage overflow desorption stirred tank, achieving three-stage continuous countercurrent lithium extraction desorption. After desorption in each overflow desorption stirred tank, the desorption solution overflows into the next-stage overflow desorption stirred tank through an overflow port. A filter screen is used at the overflow port to prevent adsorbent from overflowing with the desorption solution. The adsorbent is drawn from the bottom of the overflow desorption stirred tank to the next-stage overflow desorption stirred tank via an air lifter. By controlling the flow rate of the air lifter, it is ensured that 80% of the adsorbent in a single overflow desorption stirred tank is lifted to the next-stage overflow desorption stirred tank within 20 minutes. The desorption time of each overflow desorption stirring tank is 20 min, the stirring speed is 100 rpm, the mass ratio of desorbent to adsorbent is 4:1, the temperature is 40℃, and the pH value is controlled at around 1.5 by adding 1 mol / L HCl solution during the adsorption process of each overflow desorption stirring tank.

[0070] After desorption in the third-stage overflow desorption stirred tank, the lithium concentration of the outflowing lithium-rich solution was 1.09 g / L. After desorption in the second-stage overflow desorption stirred tank, the lithium concentration of the outflowing desorbed solution was 930.7 mg / L. After desorption in the first-stage overflow desorption stirred tank, the lithium concentration of the outflowing desorbed solution was 480 mg / L. The calculated desorption capacity of the titanium-based adsorbent particles was 5.45 mg / g, and the lithium desorption rate was 97%.

[0071] (3) Lithium-rich liquid purification and concentration process and lithium carbonate preparation process

[0072] The obtained lithium-rich solution (Li 1.09 g / L, Na 368 mg / L, K 73 mg / L, Ca 128.2 mg / L, Mg 187.9 mg / L) underwent ultrafiltration to remove suspended solids before entering the reverse osmosis concentration. After reverse osmosis concentration and subsequent nanofiltration to remove calcium and magnesium, the lithium-rich solution had a lithium ion concentration of approximately 7 g / L, a sodium ion concentration of 2.36 g / L, a potassium ion concentration of 0.47 g / L, and a combined calcium and magnesium ion concentration of 4.5 mg / L. Subsequently, the nanofiltration permeate was concentrated to 50 g / L using MVR, followed by deep resin removal of calcium, magnesium, and boron to obtain a purified solution (combined calcium and magnesium ion concentration of 2 mg / L, boron concentration of 1 mg / L). The purified solution was then subjected to lithium precipitation at 80°C using a 28% sodium carbonate solution to obtain lithium carbonate product. The lithium concentration in the lithium precipitation mother liquor was measured to be 1.31 g / L.

[0073] (4) Regeneration of titanium-based adsorbent powder attenuation

[0074] After a long cycle, when the adsorbent capacity of the titanium-based adsorbent drops to 2 mg / g, adsorbent regeneration is performed. The process involves calcining the degraded titanium-based adsorbent and mixing it with lithium carbonate. The lithium-titanium molar ratio in the mixed sample is 2:1. The uniformly mixed sample is then calcined in a muffle furnace at a temperature of about 1000℃ for 6 hours. After calcination, a lithium titanium oxide precursor is obtained, which is then activated to obtain titanium-based adsorbent powder.

[0075] Example 3

[0076] This embodiment provides a method for directly extracting lithium from salt lakes using an adsorption process, such as... Figure 1 As shown, the specific process is as follows:

[0077] (1) Countercurrent adsorption process of aluminum-based adsorbent powder

[0078] Aluminum-based adsorbent powder (the crystal form of aluminum-based adsorbent is LiCl·2Al(OH)3·nH2O) and pretreated lithium-containing brine (Li 400mg / L, Na 100g / L, K 4.16g / L, Ca 17.7g / L, Mg 1.25g / L, B 0.37g / L, Cl 190g / L, SO42-) were used. 2- 0.56 g / L, brine pH 5.8) is fed into a continuous countercurrent adsorption system containing a 3-stage overflow adsorption stirring tank (e.g., Figure 2The brine is added from the first-stage overflow adsorption stirring tank, flowing sequentially into the next-stage overflow adsorption stirring tank, and exiting from the third-stage overflow adsorption stirring tank. Unloaded adsorbent is added from the third-stage overflow adsorption stirring tank, rising sequentially to the next-stage overflow adsorption stirring tank. Loaded adsorbent is discharged from the first-stage overflow adsorption stirring tank. In this embodiment, the pretreatment employs microfiltration to remove suspended solids, colloids, macromolecules, and other components and factors that may affect downstream adsorption in the lithium-containing brine.

[0079] like Figure 6 As shown, each adsorption stage is completed by an overflow adsorption stirring tank and a plate and frame filter press. After the adsorption in each overflow adsorption stirring tank is completed, the brine and adsorbent in the upper part of each overflow adsorption stirring tank flow into the plate and frame filter press through the overflow port to complete the separation of brine and adsorbent. The filter press permeate enters the next overflow adsorption stirring tank. 55% (mass percentage) of the adsorbent after plate and frame filtration is returned to the overflow adsorption stirring tank of this stage, and 45% of the adsorbent is transferred to the previous overflow adsorption stirring tank. The adsorption time for each stage is 40 min, the stirring speed is 200 rpm, the mass ratio of brine to adsorbent is 6.75:1, and the adsorption temperature is 20℃. The filtration time for each stage is 10 min, and 40% of the adsorbent by mass is lifted from a single overflow adsorption stirring tank within 40 min. After the adsorption in the third-stage overflow adsorption stirring tank is completed, the lithium concentration of the outflowing tail brine is 55 mg / L. After the adsorption in the second-stage overflow adsorption stirring tank is completed, the lithium concentration of the brine after adsorption is 244 mg / L. After the adsorption in the first-stage overflow adsorption stirring tank is completed, the lithium concentration of the brine after adsorption is 334 mg / L. The calculated adsorption capacity of the aluminum-based adsorbent powder is 5.18 mg / g, and the lithium adsorption rate is 86.25%.

[0080] (2) Countercurrent desorption process of aluminum-supported adsorbent powder

[0081] The countercurrent desorption process of the supported adsorbent is as follows Figure 3 As shown, similar to the adsorption process, the desorption process is completed by an overflow desorption stirred tank and a plate and frame filter press. The loaded adsorbent is washed and then fed into a continuous countercurrent desorption system containing an 8-stage overflow desorption stirred tank.

[0082] The desorption solution, a low-salinity solution (reverse osmosis permeate and / or pure water), is added from the first-stage overflow desorption stirred tank and flows sequentially into the next stage overflow desorption stirred tank. The lithium-rich solution (pH approximately 5) flows out from the eighth-stage overflow desorption stirred tank. The loaded adsorbent is added from the eighth-stage overflow desorption stirred tank and gradually lifted to the next stage overflow desorption stirred tank. The unloaded adsorbent is discharged from the first stage, achieving eight stages of continuous countercurrent lithium extraction and desorption. The desorption time in each overflow desorption stirred tank is 20 minutes, the stirring speed is 200 rpm, the mass ratio of desorption solution to adsorbent is 10:1, and the temperature is 40℃.

[0083] After desorption is completed in each overflow desorption mixing tank, the desorbed liquid and adsorbent in the upper part of each overflow desorption mixing tank flow into the plate and frame filter press through the overflow port to complete the separation of the desorbed liquid and adsorbent. The desorbed liquid produced by the plate and frame filter press enters the next overflow desorption mixing tank, and all the loaded adsorbent after the plate and frame filter press is returned to the previous overflow desorption mixing tank.

[0084] After desorption in the eighth-stage overflow desorption stirred tank, the lithium concentration of the outflowing lithium-rich solution was 525 mg / L. After desorption in the seventh-stage overflow desorption stirred tank, the lithium concentration of the desorbed solution was 360 mg / L. After desorption in the sixth-stage overflow desorption stirred tank, the lithium concentration of the desorbed solution was 243.7 mg / L. After desorption in the fifth-stage overflow desorption stirred tank, the lithium concentration of the desorbed solution was 181.2 mg / L. After desorption in the fourth-stage overflow desorption stirred tank, the lithium concentration of the desorbed solution was 119.8 mg / L. After desorption in the third-stage overflow desorption stirred tank, the lithium concentration of the desorbed solution was 88.7 mg / L. After desorption in the second-stage overflow desorption stirred tank, the lithium concentration of the desorbed solution was 65.4 mg / L. After desorption in the first-stage overflow desorption stirred tank, the lithium concentration of the desorbed solution was 33.2 mg / L. The calculated desorption capacity of the aluminum-based adsorbent powder was 5.13 mg / g, and the lithium desorption rate was 99%.

[0085] (3) Lithium-rich liquid purification and concentration process and lithium carbonate preparation process

[0086] The obtained lithium-rich solution (Li 525 mg / L, Na 160 mg / L, K 13 mg / L, Ca 82 mg / L, Mg 4.5 mg / L) underwent ultrafiltration to remove suspended solids before entering the reverse osmosis concentration. After reverse osmosis concentration and subsequent nanofiltration to remove calcium and magnesium, the lithium-rich solution had a lithium ion concentration of approximately 6 g / L, a sodium ion concentration of 1.83 g / L, a potassium ion concentration of 0.15 g / L, and a combined calcium and magnesium ion concentration of 3 mg / L. Subsequently, the nanofiltration permeate was concentrated to 50 g / L using MVR, and then subjected to resin for deep removal of calcium, magnesium, and boron to obtain a purified solution (calcium and magnesium ion concentrations totaling 1 mg / L, and boron concentration of 1 mg / L). The purified solution was then subjected to lithium precipitation using a 28% sodium carbonate solution at 80°C to obtain lithium carbonate product, and the lithium concentration in the lithium precipitation mother liquor was measured to be 1.18 g / L.

[0087] (4) Regeneration of attenuated aluminum-based adsorbent powder

[0088] After a long cycle of multiple cycles, when the adsorbent capacity of the aluminum-based adsorbent powder decreases to 2 mg / g, adsorbent regeneration is performed. The process involves dissolving the degraded aluminum-based adsorbent powder with hydrochloric acid to form an AlCl3 solution, then decomposing lithium carbonate into a LiCl solution with hydrochloric acid. The two solutions are then mixed, with the lithium-aluminum molar ratio controlled at 0.5. The temperature is then raised to 75°C, and a 5 mol / L sodium hydroxide solution is added dropwise to the mixed solution, controlling the final pH to 6-7. After filtration, the solid is dried at 60°C to obtain the aluminum-based adsorbent precursor, which is then activated to obtain the aluminum-based adsorbent powder.

[0089] Example 4

[0090] This embodiment provides a method for directly extracting lithium from salt lakes using an adsorption process, such as... Figure 1 As shown, the specific process is as follows:

[0091] (1) Countercurrent adsorption process of magnetic manganese adsorbent powder

[0092] Magnetic manganese-based adsorbent powder (manganese-based adsorbent crystal form is Li) 1.6 Mn 1.6 O4) and pretreated lithium-containing brine (Li 230mg / L, Na 15.3g / L, K 2.23g / L, Ca 23mg / L, Mg 0.76g / L, B 0.71g / L, Cl 11.59g / L, SO4) 2- (19.14 g / L of brine, 3 g / L of carbonate, and a pH of 9.1) is fed into a continuous countercurrent adsorption system containing two-stage overflow adsorption stirred tanks. In each overflow adsorption stirred tank, the aeration intensity is 6 m³ / m³ of brine. 3 / h. In this embodiment, the pretreatment adopts ultrafiltration process, which aims to remove suspended solids, colloids, macromolecules and other components and influencing factors that may affect the downstream adsorption in lithium brine.

[0093] The brine is added from the first-stage overflow adsorption stirring tank and flows out from the second-stage overflow adsorption stirring tank. The unloaded adsorbent is added from the second-stage overflow adsorption stirring tank, and the loaded adsorbent is discharged from the first-stage overflow adsorption stirring tank. The adsorption time for each stage is 20 minutes, the mass ratio of brine to adsorbent is 60:1, and the adsorption temperature is 0℃.

[0094] like Figure 7As shown, each stage of adsorption is completed by an overflow adsorption stirring tank and a magnetic separator. After adsorption in each overflow adsorption stirring tank is completed, the brine and adsorbent in the overflow adsorption stirring tank are separated by a magnetic separator. The adsorbent obtained by magnetic separation is lifted to the next overflow adsorption stirring tank by the magnetic separator, while the brine enters the next overflow adsorption stirring tank through the overflow port of the overflow adsorption stirring tank. A filter screen is installed at the overflow port to ensure that the adsorbent remains in the overflow adsorption stirring tank. This ensures that 60% of the adsorbent in a single overflow adsorption stirring tank is lifted to the next overflow adsorption stirring tank within 30 minutes.

[0095] After the adsorption in the second-stage overflow adsorption stirred tank is completed, the lithium concentration of the outflowing tail brine is 47.5 mg / L. After the adsorption in the first-stage overflow adsorption stirred tank is completed, the lithium concentration of the brine after adsorption is 171 mg / L. The calculated adsorption capacity of the manganese-based adsorbent powder is 18.25 mg / g, and the adsorption rate is 79.35%.

[0096] (2) Countercurrent desorption process of magnetic manganese adsorbent powder

[0097] The countercurrent desorption process of the supported adsorbent is as follows Figure 3 As shown, similar to the adsorption process, the desorption process is completed by an overflow desorption mixing tank and a magnetic separator. In each stage of the overflow desorption mixing tank, the aeration intensity is 3 m³ / m³ of aeration per cubic meter of liquid. 3 / h.

[0098] The loaded adsorbent was washed with low-salt water and then fed into a continuous countercurrent desorption system containing two-stage overflow desorption stirred tanks. The desorption solution was a 0.1 mol / L HCl solution. The pH of the first-stage overflow desorption stirred tank was controlled to 1.5 by adding desorption solution, and the pH of the second-stage overflow desorption stirred tank was controlled to 3-4 by adding desorption solution. The lithium-rich solution flowed out from the second-stage overflow desorption stirred tank. The loaded adsorbent was added from the second-stage overflow desorption stirred tank, and the unloaded adsorbent was discharged from the first-stage overflow desorption stirred tank, realizing two-stage continuous countercurrent lithium extraction and desorption. After desorption in each overflow desorption mixing tank, the adsorbent in the overflow desorption mixing tank is lifted to the next overflow desorption mixing tank using a magnetic separator. This ensures that within 30 minutes, 80% of the adsorbent in a single overflow desorption mixing tank is lifted to the next overflow desorption mixing tank. The desorbed liquid overflows to the next stage through the overflow port at the top of the overflow desorption mixing tank. A filter screen is installed at the overflow port to ensure that the adsorbent remains in the overflow desorption mixing tank. The desorption time for each overflow desorption mixing tank is 30 minutes, the mass ratio of desorbed liquid to adsorbent is 8:1, and the desorption temperature is 10℃.

[0099] After the desorption in the second-stage overflow desorption stirred tank, the lithium concentration of the outflowing lithium-rich liquid was 1.79 g / L. After the desorption in the first-stage overflow desorption stirred tank, the lithium concentration of the desorbed liquid was 1.02 g / L. The calculated desorption capacity of the manganese-based adsorbent powder was 17.9 mg / g, and the lithium desorption rate was 98%.

[0100] (3) Lithium-rich liquid purification and concentration process and lithium carbonate preparation process

[0101] The obtained lithium-rich solution (Li 1.79 g / L, Na 206 mg / L, K 15 mg / L, Ca 185 mg / L, Mg 5.3 mg / L, Mn 83 mg / L) was subjected to oxidation to remove manganese. First, the lithium-rich solution was adjusted to pH 9 with alkali and then aerated for 30 minutes. After aeration, it was filtered using a composite filter media (comprising manganese sand and quartz sand). The manganese ion concentration in the lithium-rich solution after manganese removal was less than 1 mg / L. Suspended solids were removed by ultrafiltration before the manganese-removed lithium-rich solution entered the reverse osmosis concentration stage. After reverse osmosis concentration and then nanofiltration to remove calcium and magnesium, the lithium ion concentration was 7.5 g / L, sodium ion concentration was 0.86 g / L, potassium ion concentration was 62.8 mg / L, and the combined calcium and magnesium ion concentration was 3 mg / L. Subsequently, the nanofiltration permeate was concentrated to 50 g / L using MVR, and then purified by deep removal of calcium, magnesium and boron using resin to obtain a purified solution (calcium and magnesium ion concentrations totaling 2 mg / L, boron concentration 1 mg / L). Then, lithium was precipitated in the purified solution using a 28% sodium carbonate solution at 85°C to obtain lithium carbonate product, and the lithium concentration in the lithium precipitation mother liquor was measured to be 1.15 g / L.

[0102] (4) Regeneration of attenuated magnetic manganese adsorbent powder

[0103] After a long cycle of multiple cycles, when the adsorbent capacity of the magnetic manganese-based adsorbent powder drops to 8 mg / g, adsorbent regeneration is performed. The process involves mixing the degraded magnetic manganese-based adsorbent powder with lithium carbonate, resulting in a lithium-manganese molar ratio of 1:1 in the mixed sample. The uniformly mixed sample is then calcined in a muffle furnace at approximately 500℃ for 6 hours. After calcination, a magnetic lithium manganese oxide precursor is obtained, which is then activated to obtain the magnetic manganese-based adsorbent powder.

[0104] For those skilled in the art, various corresponding changes and modifications can be made based on the above technical solutions and concepts, and all such changes and modifications should be included within the protection scope of the claims of this invention.

Claims

1. A method for directly extracting lithium from lithium-containing brine using an adsorption process, characterized in that, Includes the following steps: Step 1: Pre-treat the lithium-containing brine to remove impurities; Step 2: The pretreated brine from Step 1 is fed into a continuous countercurrent adsorption system containing N stages of continuous overflow adsorption stirring tanks. Lithium is extracted from the lithium-containing brine through N stages of continuous countercurrent adsorption. The lithium-containing brine is added from the first-stage overflow adsorption stirring tank and flows sequentially into the next stage. Tailings flow out from the Nth-stage overflow adsorption stirring tank. Unloaded adsorbent is added from the Nth-stage overflow adsorption stirring tank and lifted sequentially into the next stage. Loaded lithium adsorbent is discharged from the first-stage overflow adsorption stirring tank. N = 2-8. The adsorbent is one or a combination of several of the following: molecular sieve-type aluminum-based adsorbents, ion sieve-type manganese-based adsorbents, and ion sieve-type titanium-based adsorbents. The adsorbent is in the form of powder, magnetic powder, or granules obtained by granulation of powder adsorbents. The particle size of the powder or magnetic powder adsorbent is 10 μm-1000 μm; the particle size of the granular adsorbent is 1000 μm-10000 μm. The lithium extraction capacity of the adsorbent in the continuous countercurrent adsorption system is adjusted by adding fresh adsorbent purchased externally or produced on-site, or by open-circuit regeneration of adsorbents with degraded performance. Step 3: Wash the loaded adsorbent discharged from the first-stage overflow adsorption mixing tank with low-salt water to remove entrained brine; Step 4: The washed loaded adsorbent from Step 3 is fed into a continuous countercurrent desorption system containing M-stage continuous overflow desorption stirring tanks. Lithium desorption is achieved through M-stage continuous countercurrent desorption. The loaded adsorbent is added from the M-stage overflow desorption stirring tank and gradually flows to the next stage. The empty adsorbent after lithium desorption is discharged from the 1-stage overflow desorption stirring tank. The desorption solution is added from the 1-stage overflow desorption stirring tank and flows into the next stage overflow desorption stirring tank. The lithium-rich solution flows out from the M-stage overflow desorption stirring tank. M = 2-8. Step 5: Return the empty adsorbent discharged from the first-stage overflow desorption mixing tank in Step 4 to Step 2 for recycling; Step 6: The lithium-rich solution obtained in Step 4 is first concentrated using reverse osmosis to produce low-salt water and concentrated water. The concentrated water is then treated with nanofiltration to remove calcium and magnesium ions. The nanofiltration permeate is further concentrated using high-pressure reverse osmosis, electrodialysis, solar cell, mechanical steam recompression, or multi-effect evaporation. The final concentrated solution is used to prepare the desired lithium product.

2. The method according to claim 1, characterized in that, In step one, the lithium-containing brine includes one or more of the following: salt lake brine, lithium-containing geothermal water, lithium-containing ore leachate, lithium-containing brine generated during oilfield extraction, and lithium-containing leachate generated during lithium battery recycling. The lithium-containing brine is of the chloride type, sodium sulfate subtype, or carbonate type, and the lithium concentration is 50-1000 mg / L. The pretreatment includes one or more of the following: sand filtration, ultrafiltration, microfiltration, flocculation sedimentation, and oxidation, and includes one or more of the following: pH adjustment, sulfate removal, carbonate removal, and heating.

3. The method according to claim 1, characterized in that, In step two, the lithium working capacity of the adsorbent is 5-50 mg / g. When the adsorption capacity of the adsorbent decreases to 25-50% of the adsorption capacity of the fresh adsorbent, an open circuit and regeneration treatment is performed. The regeneration treatment is carried out by one or more of the following methods: solid-state sintering, precipitation, and hydrothermal method.

4. The method according to claim 1, characterized in that, In step two, in each overflow adsorption stirring tank, the mass ratio of brine to adsorbent is 2-100:1, and the adsorption temperature is 0-50℃. After the brine and adsorbent are fully contacted by one or more of the following methods: mechanical stirring, aeration stirring, or pump circulation stirring, the adsorbent is separated from the brine by one or more of the following methods: concentration, bag filtration, magnetic separation, and centrifugal filtration. The separated adsorbent is lifted upwards, and the separated brine overflows downwards. The lifting rate of the adsorbent is such that the amount of adsorbent lifted in each overflow adsorption stirring tank within 1 hour is 10-80% of the total mass of the adsorbent in that overflow adsorption stirring tank. The adsorption pH in each overflow adsorption stirring tank is 5-11. Depending on the pH requirements of different adsorbents, the pH of the brine is adjusted before adsorption, or acid or alkali is directly added to each overflow adsorption stirring tank to adjust the pH of the brine.

5. The method according to claim 1, characterized in that, In step three, the total dissolved solids (TDS) content in the low-salt water is less than 1000 mg / L, including one or more of reverse osmosis permeate, surface freshwater, or evaporation condensate; the mass of the low-salt water used for washing is 1-10 times the mass of the loaded adsorbent discharged from the first-stage countercurrent adsorption tank.

6. The method according to claim 1, characterized in that, In step four, in each overflow desorption stirring tank, the mass ratio of desorbent to adsorbent is 4-40, the desorption temperature is 5-50℃, and the pH value of the desorbed solution is 2.0-7.

0. After the desorbent and adsorbent are fully mixed by one or more of the following methods: mechanical stirring, aeration stirring, and pump circulation stirring, the adsorbent and desorbent are separated by concentration, filtration, or magnetic separation. The separated adsorbent is lifted upwards, and the separated desorbent overflows downwards. In each overflow desorption stirring tank, the lifting rate of the adsorbent is such that the amount of adsorbent lifted within 1 hour is 50-300% of the total amount of adsorbent in the overflow desorption stirring tank.

7. The method according to claim 1, characterized in that, In step four, when the adsorbent is a molecular sieve type adsorbent, a low saline solution is used as the desorption solution. When the adsorbent is an ion sieve type adsorbent, an acidic solution is used as the desorption liquid. The acidic solution is prepared by mixing a low-salt water solution, a low-lithium solution, and an acid. The low-lithium solution includes one or more of the following: the washing liquid after desorption of the adsorbent, nanofiltration permeate, electrodialysis desalination water, and high-pressure reverse osmosis permeate. The acid is one or more of the following: hydrochloric acid, sulfuric acid, and nitric acid. The desorption pH in each stage overflow desorption stirring tank is 1.0-5.

0. The total dissolved solids (TDS) of the low-salinity water is less than 300 mg / L, including one or more of reverse osmosis permeate, surface freshwater, or evaporative condensate.

8. The method according to claim 1, characterized in that, In step six, the lithium-rich solution obtained in step four is pretreated before being concentrated using reverse osmosis. If the adsorbent is an aluminum-based or titanium-based adsorbent, the pretreatment of the lithium-rich solution includes the removal of suspended solids using an ultrafiltration membrane. If the adsorbent is a manganese-based adsorbent, the pretreatment of the lithium-rich solution includes adding alkali to adjust the pH to 7-9 for hydrolysis, followed by aeration oxidation for 2-30 minutes, and then filtration using composite filter media to remove manganese. After manganese removal, the manganese ion concentration in the lithium-rich solution is less than 1 mg / L. Before entering the reverse osmosis concentration stage, the lithium-rich solution after manganese removal is subjected to ultrafiltration membrane to remove suspended solids. The oxidant used for aeration oxidation is one or more of the following: air, a mixture of air and sulfur dioxide, hydrogen peroxide, oxygen, ozone, or chlorine. The composite filter media includes manganese sand and one or more of the following: activated carbon, quartz sand, fiber balls, anthracite, and ceramsite.

9. The method according to claim 1, characterized in that, In step six, the low-salt water produced by concentrating the lithium-rich solution using reverse osmosis is returned to step three for washing and / or returned to step four as desorption water. The concentrated water produced by reversing osmosis to concentrate lithium-rich solution is then subjected to nanofiltration to remove calcium and magnesium ions, resulting in a lithium ion concentration of 7-10 g / L and a combined calcium and magnesium ion concentration of less than 5 mg / L. The concentrated water obtained by further concentration of nanofiltration permeate has a lithium ion concentration of 25-50 g / L. The nanofiltration concentrate is then dialyzed to further recover lithium. The desalinated water produced by dialysis is returned to the reverse osmosis process, while the concentrated water produced by dialysis is returned to the continuous countercurrent adsorption system in step two. The concentrated solution is prepared into lithium products using evaporation crystallization, chemical precipitation, or a combination of ion exchange deep purification, bipolar membrane, and evaporation crystallization processes; the lithium products are crude, chemical-grade, or battery-grade lithium sulfate, lithium chloride, lithium carbonate, lithium phosphate, or lithium hydroxide monohydrate.

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